Using a transponder system to monitor incubation routines of Snowy Plovers

We investigated the incubation behavior of a ground-nesting shorebird, the Snowy Plover (Charadrius a. alexandrinus) by developing a transponder system that recorded the identity of parents on their nest over 24 h. The system consisted of a small chip glued on the tail of the parent, an antenna that was buried under the nest, and a recording device that was buried nearby. The transponder system was both accurate and reliable, since only 0.2% of records were false. The records of the transponder system were augmented by visual observations, and these data were analyzed by randomization tests. We found strong daily incubation routines: females incubated during the day, whereas males incubated mostly at night. Overall, the females spent significantly more time incubating the nest (11.3 h (median)/day) than the males (9.4 h/day). We discuss several hypotheses for the observed daily incubation routines of the sexes, and propose experimental studies to test these hypotheses.